Since this is a mobile application, i feel this is an essential feature. I keep it signed in to my WiFi network all the time, even when i am not in a mood to chat. This way, my friends can drop me messages without having to SMS me. But whenever i move out of the WiFi zone, the connection is lost and the messages are lost too!
To be able to be truly mobile, i would like to see a History feature, or atleast a feature to display the messages i have not read or seen yet. Carry over the unread messages of the last session to the next session please.